iant flagellar shape most often encountered in other bacteria, 

 namely the curly shape, was not observed in Listerki, nor could 

 the curly shape be induced by lowering the pH. Filamentous 

 variants could readily be obtained and these invariably retained 

 the flagellar shape of the parent nonfilamentous type. The normal 

 flagellar shape was by far the most common and was present in 

 all of the eighty motile strains studied. 



The flagella of Listeria also showed variations in function. One 

 of the original cultures had normal flagella but was entirely non- 

 motile. From two other cultures were isolated pure strains of 

 normal flagellated nonmotile individuals. Organisms with the 

 coiled flagellar shape showed fair motiHty but those with small 

 ampHtude and straight flagella showed very poor motility at best 

 and no progressive motion at all. Two variants with straight 

 flagella were obtained, one of which was entirely nonmotile while 

 the other showed only a nonprogressive wiggling and spinning 

 motion. 



On the basis of flagellar shape and function, seven varieties of 

 individuals were obtained in pure culture: nonflagellated; normal 

 flagella, motile and nonmotile; straight flagella, motile (very slight) 

 and nonmotile; coiled flagella, fair motiHty; small amplitude 

 flagella, slight motility. By plating in semisolid agar a variety of 

 flagellar mutations were observed but no new types found. The 

 rate of such mutations were calculated to be in the neighborhood 

 of 10~^ to 10~^ per cell division. 



The normal wavelength and amplitude of different strains 

 showed only minor differences. From 10 measurements on each of 

 eight strains was obtained an average wavelength of 2.01 microns 

 with a standard deviation (S.D. ) of 0.1 micron, and an average 

 amplitude of 0.48 micron with an S.D. of 0.06 micron. Based on 20 

 measurements the wavelength of the small amplitude flagella was 

 1.53 microns with amplitude 0.25 micron. For the coiled flagella 

 the wavelength was 2.18 microns and the ampHtude 0.76 micron. 



Fig. 37. a. Listeria monocytogenes. Normal flagella, peritrichous arrange- 

 ment. 



b. L. monocytogenes. Small amplitude flagella. 



c. L. monocytogenes. Straight flagella. 

 (1. L. monocytogenes. Coiled flagella. 



e. L. monocytogenes. Normal flagella. Filamentous soma. 



f. L. monocijto genes. Straight flagella. Filamentous soma. 



g. L. monocytogenes. Coiled flagella. Filamentous soma. 



a-e. From E. Leifson, and M. I.'Palen, /. Bacteriol. 70, 233-240 ( 1955). 



88 



